INTRASTROMAL CORNEAL RING SEGMENTS (ICRS, KERAVISION RING, INTACSTM): CLINICAL RESULTS AFTER 2 YEARS

Background. Since 1996 Intrastromal Corneal Ring Segments (IntacsTM, KeraVision, Inc.Fremont, Ca, USA) have been used for the correction of mild to moderate myopia at the Salzburg Eye Clinic. Aim of this study was to evaluate the stability, reversibility and adjustability for this new method.Patients and methods. Our experience and final results of 54 surgeries – 30 eyes with a minimum follow-up of 2 years – as well as the potential reversibility (3 explantations, 2 of them followed by PRK) and adjustability (3 exchanges) are reported in detail.Results. None of the eyes lost more than one line in BSCVA (in 14 of 30 eyes the BSCVA improved). 73% (22/30) eyes reached an UCVA of 1.0 or better, 47% (14/30) eyes of 1.25 or better. After 2 years 47% (14/30) eyes were within ± 0.5 Dsph of the attempted correction. We observed no significant intraor postoperative complications. After ICRS removal the refractive data returned within ± 0.75 Dsph (MRSE) and ± 0.5 Dsph (mean keratometry) of preoperative values, respectively. Patients with an ICRS exchange obtained an improved visual acuity between 0.8 and 1.0, gaining between 2 to 4 lines.Conclusions. With the follow-up period of 2 years the ICRS seem to provide a very stable correction of low to moderate myopia. The procedure is reversible to a large extent, potentially adjustable (within certain limits) and carries a minimal risk only. After explantation PRK can be performed with good visual results.</p

Ex vivo Evaluation of Tono-Pen and Pneumotonometry in Cat Eyes

Purpose: To evaluate the validity and intraobserver reliability of intraocular pressure (IOP) measurements with both pneumotonometry and the Tono-Pen in a closed ex vivo system in cat eyes. Methods: IOP was increased step by step in 5 enucleated cat eyes, while taking IOP measurements with the Tono-Pen and pneumotonometry. The outcomes were compared to readings of a digital manometer simultaneously measuring the actual pressure in the anterior chamber. Results: Pneumotonometry overestimated IOP below 15 mm Hg and underestimated pressures above 20 mm Hg. Tono-Pen tonometry considerably underestimated IOP over the whole spectrum in all of the eyes tested. The pneumotonometer was identified as the more valid and reliable instrument for cat eyes. Conclusion: Both tonometers are clinically useful tools to assess IOP for glaucoma studies using a cat animal model. However, one has to consider underestimation of IOP in the upper ranges. A correction formula can be used to calculate the actual IOP

Corneal stroma regeneration in felines after supradescemetic keratoprosthesis implantation

To show corneal regeneration in 3 cats that underwent lamellar keratectomy (90%) depth during supradescemetic keratoprosthetic implantation. Three 2-year-old cats that underwent spontaneous keratoprosthesis extrusion between 15 and 150 days after implanting a supradescemetic prosthesis into their right eyes were studied. Corneal structures and stroma thickness were evaluated by slit-lamp photographs, pachymetry, and confocal microscopy. Regenerated corneal epithelial cells, stroma matrix, and keratocyte morphology were studied with histology and transmission electron microscopy. Epithelial and stromal cell immunocharacterization was performed. Corneas progressively regained normal thickness and improved clarity within 40 to 60 days. Slit-lamp photographs and pachymetry showed gains in stromal thickness until 600 microm or more. In vivo confocal microscopy showed the restoration of normal epithelium and stroma in all cats. Corneal nerves were seen in the regenerated stroma of 2 cats. Immunostaining showed absent alpha-smooth muscle actin (SMA) expression and a keratin K3-expressing epithelium. Electron microscopy showed regeneration of normal epithelium with a well-formed basement membrane, organized corneal lamellae, and the presence of normal keratocytes. Felines are capable of regenerating corneal structures including epithelium and reinnervated stroma matrix after deep lamellar keratectomy. The use of feline models in corneal keratoprosthesis is therefore questionable

Biocompatibility of a nonpenetrating synthetic cornea in vascularized rabbit corneas

This study was designed to assess feasibility and biocompatibility of a lamellar, nonperforating supraDescemetic Synthetic Cornea (sDSC) implanted in rabbit eyes after a corneal injury. Corneal vascularization and scarring was induced in the right eye of 15 rabbits by application of 1-heptanol and complete surgical removal of the limbus. An sDSC (7-mm diameter, 450-microm-thick optical zone, 100-microm-thick outer flange) was implanted after 45 +/- 5 days. The keratoprostheses were implanted with their central optic part positioned on a completely exposed Descemet's membrane (DM) while the outer flange was located in deep stroma. Three different materials were tested: hydrophobic PMMA (n = 5) and hydrophilic HEMA-MMA (n = 5) and HEMA-NVP (n = 5) with a water content of 34% and 75%, respectively. The corneal surface was covered with a conjunctiva-Tenon flap. Central flap trephination was performed after 63 +/- 7 days. DM vascularization and scarring was assessed and graded after flap opening and weekly thereafter. In all 15 consecutive cases implantation could be completed successfully without perforation of DM. Repair of the conjunctival flap had to be performed in five rabbits. Four months postoperatively, the flaps were opened. Four of five corneas (80%) with a PMMA implant and three of five (60%) with a HEMA-NVP75 implant had retained their original transparency. The others had developed significant neovascularization in the Descemet-sDSC optic interface. All corneas (100%) that received an sDSC made of HEMA-MMA34 displayed a completely clear DM without any vessels or scarring. DM was found firmly attached to the posterior surface of the optic. Implantation of a nonperforating synthetic cornea on top of an exposed DM is feasible. HEMA-MMA34 showed the most promising results. Because opening of the anterior chamber is not required, a lamellar supraDescemetic Synthetic Cornea would theoretically reduce some of the risks attributed to penetrating keratoprostheses

Long-term follow-up of a supradescemetic keratoprosthesis in rabbits: an immunofluorescence study

To evaluate the long-term clinical and immunohistological outcome of two different non-penetrating keratoprosthesis (KPro) implanted in non-injured rabbit corneas. Three rabbits underwent implantation of a pHEMA-MMA(34) synthetic cornea in the supradescemetic space, and PMMA synthetic corneas in the supradescemetic space and within the central stroma. Animals were followed for at least 24 months before euthanasia. Periodic evaluation was performed with slit-lamp examination and photography. At the end of the follow-up, histological examination including hematoxylin eosin staining and immunocharacterization against collagen IV, alpha smooth muscle actin (α-SMA) and macrophages was performed. The pHEMA-MMA(34) implant was not extruded, and remained transparent until the end of follow-up. This material did not induce any cell infiltration, corneal scarring or tissue remodeling in the surrounding stroma as shown by immunofluorescence. In contrast, synthetic corneas made of PMMA-induced myofibroblast differentiation, stromal remodeling and macrophage infiltration. This reaction was even more significant in the rabbit with the PMMA implant within the corneal stroma. pHEMA-MMA(34) was clinically biocompatible, and did not induce any inflammatory reaction or scarring when implanted in the supradescemetic space. This material showed more promising biocompatibility results than for PMMA, whether implanted within the central cornea stroma or in the supradescemetic space

Pharmacological targeting of membrane rigidity: implications on cancer cell migration and invasion

The invasive potential of cancer cells strongly depends on cellular stiffness, a physical quantity that is not only regulated by the mechanical impact of the cytoskeleton but also influenced by the membrane rigidity. To analyze the specific role of membrane rigidity in cancer progression, we treated cancer cells with the Acetyl-CoA carboxylase inhibitor Soraphen A and revealed an alteration of the phospholipidome via mass spectrometry. Migration, invasion, and cell death assays were employed to relate this alteration to functional consequences, and a decrease of migration and invasion without significant impact on cell death has been recorded. Fourier fluctuation analysis of giant plasma membrane vesicles showed that Soraphen A increases membrane rigidity of carcinoma cell membranes. Mechanical measurements of the creep deformation response of whole intact cells were performed using the optical stretcher. The increase in membrane rigidity was observed in one cell line without changing the creep deformation response indicating no restructuring of the cytoskeleton. These data indicate that the increase of membrane rigidity alone is sufficient to inhibit invasiveness of cancer cells, thus disclosing the eminent role of membrane rigidity in migratory processes

Development of body lengths and muscle mass.

<p>(A) Total body lengths of normal-sized fish (NF, open bars) and dwarf fish (DF, dashed bars) imprinted at 2 (blue) and 6°C (red) at the end of the imprinting period (0 dph) and in the juvenile stage (80 dph). Values at bottom of bars provide number of individuals included in length measurement. Total fast (B) and slow (C) muscle csa in one half of the trunk (8 individuals per thermal group of each ecotype); whiskers indicate s.e., significant differences are assigned at p≤0.05 (*). (D) Correlation of slow muscle relative proportion (fast-to-slow muscle ratio) with fish size as given by total muscle csa; regression line equations: NF-2: y = 7.3x + 3.9 (r² = 0.87), NF-6: y = 12.2x + 7.6 (r² = 0.95), DF-2: y = 11.7x + 7.2 (r² = 0.94), DF-6: y = 15.9x + 10.3 (r² = 0.97).</p

Quantification of muscle precursor cells (MPCs).

<p>Numbers of labelled cells (means + s.e.) in double-immunostained 10 μm myotomal cross-sections of fish of the normal-sized form (NF, open bars) and dwarf fish (DF, dashed bars) imprinted at 2° (blue) and 6°C (red) at hatching and at 80 dph. Values at bottom of bars provide total numbers of evaluated quadrants (fish at hatching) and somite/myotome areas delimited by 2 successive myosepta (fish at 80 dph), respectively. Data at hatching derived from 16 2°-fish and 6°- fish each in the normal form, and from 8 2°-fish and 6°-fish each in the dwarf form; data at 80 dph derived from 7 individuals in all four groups. (A) Total numbers of Pax7+ cells per 100 μm distance within the DM and the lateral fast muscle. (B,C) Percentages of Pax7+ cells that have entered proliferation (Pax7+/H3P+) (B) or differentiation (Pax7+/Mgn+) (C). (*) Intergroup differences significant at p≤0.05.</p